Real group velocity in a medium with dissipation

L. Muschietti; C. T. Dum

doi:10.1063/1.860877

Body waves as normal and leaking modes—leaking modes of Love waves

Bulletin of the Seismological Society of America ◽

10.1785/bssa0640020301 ◽

1974 ◽

Vol 64 (2) ◽

pp. 301-306

Author(s):

B. J. Radovich ◽

J. Cl. De Bremaecker

Keyword(s):

Group Velocity ◽

Half Space ◽

Normal Modes ◽

Brewster Angle ◽

Body Waves ◽

Love Waves ◽

Wave Number ◽

Phase Velocities ◽

Real Group ◽

Group Velocities

abstract Dispersion curves of leaking modes of Love waves are computed for a one-layer crust-mantle model. The frequency and wave number are complex, but the group velocity is purely real. Group velocities well below the Airy phase of normal modes are found; waves with group velocities between 1.0 and 3.8 km/sec attenuate the least, but even these decay too much ever to be detected. There are no phase velocities between the velocity of the half-space and that corresponding to the Brewster angle.

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Wave packets, rays, and the role of real group velocity in absorbing media

Physical Review E ◽

10.1103/physreve.57.1005 ◽

1998 ◽

Vol 57 (1) ◽

pp. 1005-1016 ◽

Cited By ~ 19

Author(s):

Elazar Sonnenschein ◽

Igor Rutkevich ◽

Dan Censor

Keyword(s):

Group Velocity ◽

Wave Packets ◽

Real Group ◽

Absorbing Media

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Interferometric (Fourier-Spectroscopic) Measurement of Electron Energy Distributions

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100134144 ◽

1990 ◽

Vol 48 (2) ◽

pp. 110-111 ◽

Cited By ~ 1

Author(s):

F. Hasselbach ◽

A. Schäfer

Keyword(s):

Group Velocity ◽

Wave Packets ◽

Index Of Refraction ◽

Electron Wave ◽

Fringe Contrast ◽

Faraday Cage ◽

Optical Index ◽

Wien Filter ◽

Coherent Wave ◽

Electric And Magnetic Fields

Möllenstedt and Wohland proposed in 1980 two methods for measuring the coherence lengths of electron wave packets interferometrically by observing interference fringe contrast in dependence on the longitudinal shift of the wave packets. In both cases an electron beam is split by an electron optical biprism into two coherent wave packets, and subsequently both packets travel part of their way to the interference plane in regions of different electric potential, either in a Faraday cage (Fig. 1a) or in a Wien filter (crossed electric and magnetic fields, Fig. 1b). In the Faraday cage the phase and group velocity of the upper beam (Fig.1a) is retarded or accelerated according to the cage potential. In the Wien filter the group velocity of both beams varies with its excitation while the phase velocity remains unchanged. The phase of the electron wave is not affected at all in the compensated state of the Wien filter since the electron optical index of refraction in this state equals 1 inside and outside of the Wien filter.

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The Value of Subjective Appreciation in the Medical Record – II. The Evalution of the General Condition of the Patient

Methods of Information in Medicine ◽

10.1055/s-0038-1636620 ◽

1978 ◽

Vol 17 (02) ◽

pp. 103-105

Author(s):

D. Lahaye ◽

D. Roosels ◽

J. Viaene

Keyword(s):

Medical Record ◽

General Condition ◽

Normal Weight ◽

Group Differences ◽

Computer File ◽

Real Group ◽

Empiric Data ◽

Medical Examinations ◽

Lower Limits

Based on the analysis of 13,110 medical examinations performed on a standardized population of pneumoconiosis patients recorded on the F.O.D. computer file, the authors describe the value of the subjective estimations of »obesity«, »thinness« or »normal weight« by their correlation with the observed weight and height. Although there are striking differences in appreciation between the physicians performing the examinations, the qualifications »obese«, »thin« or »normal« correspond with real group differences in weight, between certain limits which can be defined. The ratio between the observed weight and the expected weight (using the Broca formula) shows the same pattern. In tins way it becomes possible to propose upper and lower limits for obesity, thinness and normal weight based on purely empiric data. Feeding back this information to the examining physicians should help reduce the differences between physicians and improve the results. Therefore, the authors find it useful to keep such information in the computer file.

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